Stay-bolt for steam-boilers.



Patented Jan. 2, "I900.

No. 640,66l.

. F. W. JOHNSTONE.

STAY BOLT FOR STEAM BOILERS. (Application filed June 12, 1899.)

(No Modal.)

I WITNESSES:

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UN TED STATES PATENT omce.

FRANCIS W. JOHNSTONE, OF MEXICO, MEXICO.

STAY-BOLT FOR STEAM-BOILERS;

SPECIFICATION formingm of Letters Patent No. 640,661, dated January 2,1960. Application filed June 12, 1899. Serial INC-720,313. (No model.)

To all whom, it 'may concern:

Be it known thatI, FRANCIS W. J OHNSTONE,

a citizen of the United States, residing at the city of Mexico, in theRepublic of Mexico, have invented a certain new and useful Improvementin Stay-Bolts for Steam-Boilers, of which improvement the following is aspecification.

Myinvention relates to the staying of sheets of locomotive and othersteam boilers for the purpose of opposing proper and sufficientresistance to the exertion of internal pressure; and its object is toenable this result to be effectively attained, more particularly inboilers working under comparatively high pressures, in such manner andby such means as will be readily and desirably applicable in connectionwith steam-boilers of various designs known in the art and will inpractice afiord a substantial safeguard against the breakage ofstay-bolts by the expansion of the sheets in which they are secured.

To this end my invention, generally stated, consists in the combination,in a flexible staybolt, of a stem or body, a spherical head formedthereon, a correspondingly-socketed plug embracing the head, andscrew-threads for connecting the stem and plug to an inner and an outersheet of a steam-boiler.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawings, Figure 1 is a transverse section throughthe water-space of a steam-boiler, illustrating a flexible stayboltembodying my invention as preliminarily connected to the boiler-sheets;Fig. 2, a similar section showing the stay-bolt as finally secured inoperative condition to the sheets; Fig. 3, a similar sectionillustrating a staybolt having the capacity of flexibility at each ofits ends as preliminarily connected to the boiler-sheets; Fig. 4, asimilar section showing the stay-bolt 0f Fig. 3 as finally secured inoperative condition to the sheets; Fig. 5, a longitudinal centralsection through the socketed plug in its original condition, and Fig.6an end view of the same.

The loss of life and destruction of property occasioned by explosions oflocomotive-boilers have been recognized as being largely due to thebreakage of stay-bolts, the liability to which is materiallyinoreased byreason of the adoption of high steam-pressures in the opera tion oflocomotive-engines of the later and approved types which are now ingeneral use on the railroads of the United States and other countries.Notwithstanding careful and frequent inspections the risk of explosionsfrom broken stay-bolts continues to be a serious and a dangerous one,and it is of material importance in the operation of railroads that thisrisk should be minimized by the adoption of such safeguards as may beproduced and be found effective to that end, as well as by theemployment of material and workmanship of the highest grade obtainable.Experience has shown that in the great majority of instancesbreakage ofstay-bolts occurs near the inside of the outer sheet, and it is clearlydue to the fact that'the rigid connection of the stay-bolt to the outersheet prevents it from yielding or moving relatively to the sheet inaccordance with the movements of the latter under the expansive actionof applied heat. My invention provides a yielding or flexible connectionof the stay-bolt with the outer sheet, as well as with the inner sheet,if desired, and the strains which are exerted upon stay-bolts of theordinary construction by the expansion of the sheet or sheets arethereby avoided.

The construction and manner of application of my invention render itadvantageously adaptable,without materialincrease of cost ormodification of other structural elements, to use in locomotive andother steam boilers of any of the standard types of present practice.

Referring first to Figs. 1, 2, 5, and 6,- in the practice of myinvention I provide a staybolt having a cylindrical stem or body 1,corresponding in diameter with stay-bolts of the ordinary construction,upon one end of .which is formed what is ordinarily termed a sphericalhead 2 or, in exact terms, one which varies from a true sphere only inso far as is due to its junction with the cylindrical body of the boltthroughout the full transverse area thereof. The outer end of the body 1is squared for a sufficient distance to afford proper bearing for awrench, and a screwthread 3 is out upon the body for a sufficient IOO 35liminarily connected to the sheets.

of the body is such that when the screwthread 3 is engaged with theinner sheet 4 and a sufiicient length of the thread projects beyond theouter side of said sheet to be riveted 5 over thereon a portion of thehead 2 of the bolt will stand within an opening in the outer sheet 5,which receives a socketed plug 6, by which the bolt is connected to saidouter sheet. The plug 6, which is preferably made of cast-steel, isreamed out to provide a socket 7, within which the head 2 can neatlyfit, and is slightly tapered or in the form of a frustum of a cone, thelesser diameter of which is next the open end of the socket 7. A. beador I 5 strengthening-lip 8is formed around the end of the socket, and acentral stem 9, having a squared end portion to receive a wrench, isformed on the opposite end of the plug.

The bolt 1 and plug 6 are connected one to the other and secured to theboiler-sheets 4 5 in the following manner: The plug 6 having been heatedto a degree proper to enable it to be worked, the head 2 of thestay-bolt l is inserted in the socket 7 and the shell sur- 2 5 roundingthe socket is closed down upon the head bya hammer and suitable dies,the bolt being thus held in and spherically jointed to the plug. Ascrew-thread 10 is then out upon the tapered portion of the periphery ofthe plug and is engaged with acorresponding insheets 4 and 5,respectively, and their connection therewith completed, as shown in Fig.2. It will be seen that relative movement of the outer sheet 5 and thestay-bolt body 1, including rotation of the head in the socket,

is freely permitted by reason of the connection of the sheet andstay-bolt through a true universal joint, and the sheets are at the sametime held together with the same resistance to internal pressure as itan ordinary 5o stay-bolt rigidly connected to each of them wereemployed.

I have ascertained by experimental test that a seven-eighths-inchstay-bolt will break under a sufficient applied strain without beingpulled out of a'plug to which it is connected in the manner abovedescribed.

Under certain conditions of service it may be found desirable andadvantageous to provide a stay-bolt each end of which is connectedflexibly or through a universal joint with the adjacent boiler-sheet,and my invention may, as shown in Figs. 3 and 4, be so applied withoutdeparture from its essential and governing features. To this end aspherical head 2 is formed upon each end of the body 1 of the stay-bolt,and a socketed plug 6 is connected to each of the heads in the mannerabove described. The plugs 6 Gare preliminarily connected to theboiler-sheets 4 5 by I the engagement of their screw-threads 10 withcorresponding internal threads in the sheets, as shown in Fig. 3, andthe stems 9 of the plugs are then out oft and the plugs riveted over onthe sheets, completing their connection therewith, as shown in Fig. 4.As in the instance first described, each end of the staybolt' is securedto the adjacent boiler-sheet by screw-thread connections and the sameuniversal-joint device is employed, this being in the instance lastdescribed applied similarly at the connection of the bolt with each ofthe sheets.

It will be obvious that while I have herein set forth the application ofmy invention in connection with steam-boilers, for which it is primarilyand chiefly designed, it is equally adaptable to use in the constructionof tanks, reservoirs, or other structures in which metal sheets areemployed, forming the walls of spaces within which pressure is or may beexerted and which are subject to deformation or change of relativeposition due to contraction and expansion or to any other cause.

I am aware that a stay-bolt has been here tofore proposed having anangular head projectin g beyond the outer sheet of a boiler and fittingin a closed cap in which it is held without the capacity of rotation,the cap being connected to the sheet by screw-threads surrounding atapered central passage which incloses a portion of the body of thestay-bolt. Inasmuch as this construction may afiord a certain degree offlexibility, although failing to provide a truly universal joint, Ihereby disclaim, broadly, a stay-bolt which is flexibly connected orjointed to a boiler-sheet.

I claim as my invention and desire to secure by Letters Patent-- 1. Thecombination of astay-bolt havinga stem or body and a spherical head, aplug having a correspondingly-formed socket embracing the head of thestay-bolt, and screwthreads for connecting the stay-bolt and thesoclreted plug to an inner and an outersheet of a steam-boiler.

2. The combination of a stay-bolt having a stem or body with a sphericalhead at one end and an external screw-thread adjoining its opposite end,and a plug having a spherical socket embracing the head of thestay-bolt, and having an external screw-thread on its body surroundinga. portion of the socket thereof.

3. The combination of a stay-bolt having a stem or body with a sphericalhead at one end, a squared projection at the opposite end, and anexternal screwthread adjoining said squared projection, and a plughaving a spherical socket embracing the head of the stay-bolt, andhaving an external screwthread on its body surrounding a portion of thesocket thereof and a central squared projection on its end farther fromthe socket.

i. The combination of a stay-bolt having a its 10 spectively.

5. A plug for receiving and connecting a flexible stay-bolt to aboiler-sheet, having a cylindrical socket with a hemispherical bottom,the open end of said plug being adapted to be closed down upon aspherical head on a stay-bolt, and a central projection on its endfarther from the opening of the socket.

FRANCIS WV. JOHNSTONE.

Witnesses:

LoUIs P. SCHAEFER, WM. S. HARRIS.

